From 1027e5372ff2f0d16b7fe177f1eae72bffc034e3 Mon Sep 17 00:00:00 2001
From: Pranav K <prkrishn@hotmail.com>
Date: Fri, 14 Feb 2020 08:34:23 -0800
Subject: [PATCH] Use the analyzer from the SDK when available (#18885)

* Use the analyzer from the SDK when available

This prevents a build warning when building a project that contains a reference to
Microsoft.AspNetCore.Components and a netcoreapp3.0 or newer targeting Web project.

The Web SDK implicitly adds the Components.Analyzer for netcoreapp3.0 or newer targeting projects.
If the project additionally referenced this package (directly or transitively), the package would
set up a property that prevented the implicit analyzer reference. This prevented the analyzer from
being referenced twice.

There were two issues with the current approach:

a) The props file wasn't propogated via buildTransitive. Consequently transitive project references
would reference two copies of the analyzer. When these were different versions, it resulted in a compiler
warning.

b) Forward looking, this prevents newer versions of the analyzer shipped from the SDK from ever being used.
This is particularly problematic since apps are likely to reference component libraries that were previously
compiled against 3.x.

This change attempts to mitigate both of these issues:

a) We add a buildTransitive so our build targets flow
b) We knock out the analyzer added by the package if the SDK's already added it.

Fixes https://github.com/dotnet/aspnetcore/issues/18563

* Update Microsoft.AspNetCore.Components.Analyzers.targets

* Update Microsoft.AspNetCore.Components.Analyzers.targets

* Add a description

* Update Microsoft.AspNetCore.Components.Analyzers.targets
---
 ...oft.AspNetCore.Components.Analyzers.csproj |  1 +
 ...soft.AspNetCore.Components.Analyzers.props |  5 ---
 ...ft.AspNetCore.Components.Analyzers.targets | 34 +++++++++++++++++++
 ...ft.AspNetCore.Components.Analyzers.targets |  3 ++
 4 files changed, 38 insertions(+), 5 deletions(-)
 delete mode 100644 src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.props
 create mode 100644 src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets
 create mode 100644 src/Components/Analyzers/src/buildTransitive/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets

diff --git a/src/Components/Analyzers/src/Microsoft.AspNetCore.Components.Analyzers.csproj b/src/Components/Analyzers/src/Microsoft.AspNetCore.Components.Analyzers.csproj
index a83904f245..903de47c78 100644
--- a/src/Components/Analyzers/src/Microsoft.AspNetCore.Components.Analyzers.csproj
+++ b/src/Components/Analyzers/src/Microsoft.AspNetCore.Components.Analyzers.csproj
@@ -18,6 +18,7 @@
   <ItemGroup>
     <None Include="$(TargetPath)" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
     <None Include="build/netstandard2.0/*" Pack="true" PackagePath="build/netstandard2.0" />
+    <None Include="buildTransitive/netstandard2.0/*" Pack="true" PackagePath="buildTransitive/netstandard2.0" />
   </ItemGroup>
 
 </Project>
diff --git a/src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.props b/src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.props
deleted file mode 100644
index 0ba7b4da05..0000000000
--- a/src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.props
+++ /dev/null
@@ -1,5 +0,0 @@
-<Project>
-  <PropertyGroup>
-    <DisableImplicitComponentsAnalyzers>true</DisableImplicitComponentsAnalyzers>
-  </PropertyGroup>
-</Project>
diff --git a/src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets b/src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets
new file mode 100644
index 0000000000..d8c68fd5ee
--- /dev/null
+++ b/src/Components/Analyzers/src/build/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets
@@ -0,0 +1,34 @@
+<Project>
+  <!--
+  The Web.SDK unconditionally adds the components analyzer to all qualifying Web projects. A project qualifiies if it targets netcoreapp3.0 or later and does not have a flag that
+  prevents the implicit analyzer from being added. We want to ensure that when a Web project also references this package, typically as the result of referencing a component class library,
+  the analyzer in the SDK always wins.
+
+  "ResolvedAnalyzers" contains the list of analyzers that are resolved from package references. "Analyzer" contains the list of of analyzers used by the compiler.
+  The ResolveLockFileAnalyzers target copies items from ResolvedAnalyzers to Analyzer.
+
+  The target below runs before ResolveLockFileAnalyzers executes. If it discovers that the Analyzer item group was previously populated by the WebSDK, it prevents the analyzer from the package
+  from being used by removing it from the ResolvedAnalyzers list.
+
+  Note: Prior to 3.1.3, this package prevented the analyzer from the SDK from being used by setting DisableImplicitComponentsAnalyzers=true. This would have prevented newer versions of the analyzer
+  from the SDK from ever being used. A compilation of SDK and package version combinations:
+
+  Package Version         SDK Version     Result
+  ==================================================
+  Earlier than 3.1.3      Any            Package wins
+  3.1.3 or newer          Any            SDK wins
+  -->
+  <Target Name="_RemoveComponentAnalyzer" BeforeTargets="ResolveLockFileAnalyzers" Condition="'@(Analyzer->Count())' != '0'">
+    <ItemGroup>
+      <_AspNetCoreComponentsAnalyzerName Include="$([System.IO.Path]::GetFileNameWithoutExtension('%(Analyzer.Identity)'))" />
+    </ItemGroup>
+
+    <PropertyGroup>
+      <_AspNetCoreComponentsAnalyzerPath>$([MSBuild]::NormalizePath('$(MSBuildThisFileDirectory)../../analyzers/dotnet/cs/Microsoft.AspNetCore.Components.Analyzers.dll'))</_AspNetCoreComponentsAnalyzerPath>
+    </PropertyGroup>
+
+    <ItemGroup Condition="'@(_AspNetCoreComponentsAnalyzerName->AnyHaveMetadataValue('Identity', 'Microsoft.AspNetCore.Components.Analyzers'))' == 'true'">
+      <ResolvedAnalyzers Remove="$(_AspNetCoreComponentsAnalyzerPath)" />
+    </ItemGroup>
+  </Target>
+</Project>
diff --git a/src/Components/Analyzers/src/buildTransitive/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets b/src/Components/Analyzers/src/buildTransitive/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets
new file mode 100644
index 0000000000..fd79fdac66
--- /dev/null
+++ b/src/Components/Analyzers/src/buildTransitive/netstandard2.0/Microsoft.AspNetCore.Components.Analyzers.targets
@@ -0,0 +1,3 @@
+<Project>
+  <Import Project="..\..\build\netstandard2.0\Microsoft.AspNetCore.Components.Analyzers.targets" />
+</Project>